The invention relates generally to pulse laser tracking. In particular, this invention provides signal integration to distinguish a weak measured pulse reflected from a target against strong background noise.
A missile or projectile aimed at a target may include a targeting laser designator and a detector to receive reflected laser energy from the target. That reflection may be used to provide course correction information for terminal guidance to the target.
Historically, the development of laser guided weapons began in the early 1960s. Two methods of missile guidance included a beam-rider that follows the laser beam to the target and semi-active guidance that directs to the reflected energy off the target. Semi-active guidance was and remains preferred over the beam-rider due to the former's advantage in releasing the weapon from a location beyond the target's line-of-sight.
Initially, guidance processors for laser guidance weapons used analog electronics. Inertial sensors were bulky and expensive and thus not employed for these purposes. Even had inertial sensors been available, the computations involved in strap-down guidance would have been impossible in the volume and weight constraints available in a missile or bomb. With the advent of expendable, miniature and powerful processors, as well as inexpensive tactical-grade sensors, guidance algorithms can be much more capable and robust. Some guided weapons use the Global Positioning System (GPS) for positional updates at a one-second rate.
Over the past several years, the armed services have indicated a desire to replace the wavelength used by laser-guided weapons from the non-eye-safe 1.06 μm (1060 nm) near-infrared wavelength to the eye-safe 1.54 μm (1540 nm) mid-infrared eye-safe wavelength. The longer wavelength has the additional advantages of (a) corresponding to less atmospheric attenuation, and (b) greater sensitivity for its detectors. Despite these advantages, converting to the longer wavelength has encountered opposition because of sunk costs associated with the existing designators and munitions that employ the shorter wavelength. The anticipated cost of replacing both munitions and designators is considered prohibitive, thereby rendering equipment conversion impractical under conventional circumstances.